VLT/FORS spectroscopy of faint cataclysmic variables discovered by the Sloan Digital Sky Survey |
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| Authors: | John Southworth B T Gänsicke T R Marsh D de Martino P Hakala S Littlefair P Rodríguez-Gil P Szkody |
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| Institution: | Department of Physics, University of Warwick, Coventry CV4 7AL;INAF –Osservatorio di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy;Observatory, University of Helsinki, PO Box 14, Helsinki, Finland;Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH;Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain;Astronomy Department, University of Washington, Seattle, WA98195, USA |
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| Abstract: | We present medium-resolution VLT/FORS2 spectroscopy of six cataclysmic variables (CVs) discovered by the Sloan Digital Sky Survey (SDSS). We determine orbital periods for SDSS J023322.61+005059.5 (96.08 ± 0.09 min), SDSS J091127.36+084140.7 (295.74 ± 0.22 min), SDSS J103533.02+055158.3 (82.10 ± 0.09 min) and SDSS J121607.03+052013.9 (most likely 98.82 ± 0.16 min, but the one-day aliases at 92 and 107 min are also possible) using radial velocities measured from their Hα and Hβ emission lines. Three of the four orbital periods measured here are close to the observed 75–80 min minimum period for CVs, indicating that the properties of the population of these objects discovered by the SDSS are substantially different to those of the CVs found by other means. Additional photometry of SDSS J023322.61+005059.5 reveals a periodicity of approximately 60 min which we interpret as the spin period of the white dwarf, suggesting that this system is an intermediate polar with a low accretion rate. SDSS J103533.02+055158.3 has a period right at the observed minimum value, a spectrum dominated by the cool white dwarf primary star and exhibits deep eclipses, so is an excellent candidate for an accurate determination of the parameters of the system. The spectroscopic orbit of SDSS J121607.03+052013.9 has a velocity amplitude of only 13.8 ± 1.6 km s−1 , implying that this system has an extreme mass ratio. From several physical constraints we find that this object must contain either a high-mass white dwarf or a brown-dwarf-mass secondary component or both. |
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| Keywords: | binaries: eclipsing stars: individual: SDSS J023322 61+005059 5 stars: individual: SDSS J091127 36+084140 7 stars: individual: SDSS J103533 02+055158 3 stars: individual: SDSS J121607 03+052013 9 novae cataclysmic variables |
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